The University of El Salvador, located in San Salvador, is the only public university in the country. It spends $60 million a year to teach 50,000 students, and its budget is so limited that it can only accept about one-third of applicants. (By comparison, the University of Michigan, which has a similar number of students, spends $1.3 billion.) Protests over the shortage of spots regularly shut down the campus. Semesters don't end on time. U.S. News & World Report ranks it 68th in Latin America.

Martinez says the arrival of MOOCs is adding to an already "huge pressure" to improve the university. And early data on the new Web classes suggest they may have similar impacts elsewhere. Coursera, the largest MOOC company, reported in August that of its first million users, 62 percent were from outside the U.S., led by students in Brazil, India, China, and Canada.

So far, students are coalescing around such classes in ways that are improvised and ad hoc. Some are using online bulletin boards to arrange study groups at cafés in cities like Shanghai and Madrid. "We do hope that people grab these classes and build on them," says Anant Agarwal, the head of edX and the teacher whose voice is heard narrating the electronics class. He even imagines overseas "educational dormitories" springing up, where some entrepreneur might charge for food and a bed and perhaps supply a teaching assistant to help with classwork.

In several cases, enterprising teachers have taken the lead. A U.S. graduate student, Tony Hyun Kim, used edX last spring to teach high school students in Ulan Bator, the capital of Mongolia. A dozen passed the course. After hearing about it, the National University of Mongolia sent several deans on a mission to visit Agarwal at edX's offices in Cambridge, Massachusetts.

While MOOCs could be an opportunity to improve education in poor regions, they're also profoundly threatening to bad professors and to weak institutions.